**4. Conclusions**

This paper presented a numerical investigation of the effects of modifications along the leading edge of a damaged rotor blade on the flow field and heat transfer characteristics in a 1.5-stage GE-E<sup>3</sup> gas turbine. This is the first study in which the effects of different damage locations of a turbine blade are examined. We analyzed five cases of rotor blades—an undamaged blade as reference and blades damaged at the top and middle on the pressure and suction sides.

The results confirmed that:


sudden increase. The heat flux on the S2 vane surface considerably increased around the mid-span on the pressure side and around the hub and tip on the suction side. *This led to an increase in the local thermal stress, showing a potential reduction in the fatigue life of the blade and the vane which would increase the maintenance costs*.

− Moreover, the *modifications to the top-damaged blades enhanced the aerodynamic and total-to-total e*ffi*ciencies, while the same for the middle-damaged blades caused reductions in the e*ffi*ciencies.*

This study investigated the e ffects of modification at various locations along the leading edge of the rotor blades. Hence, additional studies should be conducted on damage at other locations, such as the center and trailing edge of the blade, to provide a comprehensive overview of the e ffects of damage on the flow field, heat transfer, and aerodynamic performance of a gas turbine. This could provide more insight for design engineers to develop better cooling methods to enhance the fatigue life of the blades and vanes of gas turbines. Moreover, the findings of this study can facilitate damage or failure detection in gas turbines through monitoring of sudden changes in pressure and temperature fields.

**Author Contributions:** Conceptualization, methodology, investigation: T.D.M. and J.R.; validation, formal analysis, writing—original draft preparation, visualization: T.D.M.; writing—review and editing, supervision, project administration, funding acquisition: J.R. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) gran<sup>t</sup> funded by the Korea governmen<sup>t</sup> (MOTIE) (20193310100060, Evaluation of the performance for F-class or more gas turbine blade prototype). This research was supported by Korea Electric Power Corporation (Grant number: R19XO01-39). This research was supported by the MSIT (Ministry of Science and ICT), Korea, under the ITRC (Information Technology Research Center) support program (IITP-2020-2020-0-01655) supervised by the IITP (Institute of Information & Communications Technology Planning & Evaluation).

**Conflicts of Interest:** The authors declare no conflict of interest.
